Printing Machinery Questions and Answers

Answer: C

Correct answer: 2 - 4 - 1 - 3

The order is set by what each step requires. The paste is printed, then dried so the print is not smudged in handling, then steamed so that moisture and heat let the dye migrate into the fibre and react with it, and finally washed to remove the thickener and any dye that did not fix. Steaming before drying would blur the design, and washing before fixing would remove the dye entirely.

Answer: D

Without a thickener the paste would wick along the yarns and the design would lose its edges. The thickener has to be washed out afterwards, which is a significant part of the water use in printing. Sharp edges are what a good thickener delivers.

Answer: A

Both are true and the reason gives the requirement: high viscosity at rest holds the outline while low viscosity under shear lets the paste pass the screen, and the two demands can only be met by a shear thinning paste.

Answer: B

Correct answer: 1 and 2 only

Statements 1 and 2 describe the rheology a print paste needs: shear-thinning under the squeegee so it flows through the screen, and rapid recovery once on the cloth so it stays where it was placed. Statement 3 is the opposite of what is wanted - a Newtonian paste has the same viscosity at every shear rate, so it would either be too stiff to print or too thin to hold the line.

Answer: C

Starch reacts with the dye and fixes it to the thickener rather than the fibre, so alginate is used instead. This is one of the few cases where the thickener chemistry is dictated by the dye class. Alginate is the standard choice for reactives.

Answer: D

Both are true and the reason gives the necessity: a starch thickener would consume dye and leave a stiff, poorly fixed print, so the choice of thickener is part of the dye selection. Starch is fine for pigment or vat printing.

Answer: A

Correct answer: False

Starch carries hydroxyl groups, and a reactive dye reacts with hydroxyls - that is how it bonds to cotton. A starch thickener would therefore consume a large part of the dye and the reacted thickener would be difficult to wash out, leaving a stiff handle and poor fastness. Sodium alginate is used instead, having no reactive hydroxyls available to the dye.

Answer: B

It gives extremely sharp definition and needs no washing off, but it works only on polyester and similar synthetics. The dye must sublime, which restricts it to the disperse class. Definition is the sharpest of any method.

Answer: C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the limitation. Transfer printing works by subliming disperse dye from paper into the fibre under heat, and disperse dyes have affinity only for hydrophobic synthetics - principally polyester. Cotton offers them nothing to dissolve into, so the process cannot be used on it without first coating the fabric.

Answer: D

Digital printing places the ink directly from a print head with no image carrier at all. The other three all need an engraved or exposed image, which is where their setup cost lies. Setup cost is what decides the economics.